In its investigation into whether classified information was sent using Hillary Clinton’s private email server, the FBI is reportedly looking at whether aides to the former secretary of state retyped information from classified sources into emails then sent to Clinton’s unsecured system.

In their investigation, F.B.I. agents have sought to compare electronic timestamps on classified sources to figure out whether the aides reviewed the sources and then retyped the information into emails that were sent or forwarded to Mrs. Clinton’s private server. That has proved challenging, and one official said investigators have not concluded that such retyping occurred. State Department officials said that an employee who divulges classified information in the department’s unclassified network could face administrative punishments, including reprimands or in severe cases the loss of any security clearance.

According to multiple reports Wednesday, the FBI investigation into Clinton’s email setup turned to whether a crime was committed in the mishandling of classified information. As it concludes the probe, the FBI could move to question Clinton and her top aides about the private server, both the Times and the Washington Postreported.

One of Clinton’s former State Department staffers, Bryan Pagliano, is already cooperating with the FBI and has been granted immunity by the Justice Department. Pagliano set up Clinton’s private server in her Chappaqua, New York, home in 2009.

Clinton’s presidential campaign has been dogged by inquiries into her use of private email at the State Department, which was revealed about a year ago. Her campaign has characterized the FBI investigation as a "security inquiry" and dismissed the email controversy as the result of a partisan effort to hurt her presidential run.

While Clinton and the State Department have said that none of the emails on her system were marked classified when they were sent or received, more than 2,000 messages have been upgraded to classified in the agency’s review of the emails. Twenty-two of the messages have been deemed top secret, causing the State Department to withhold them from public release. The agency has said that it is looking into whether those messages held classified material when they originated on Clinton’s email.

The FBI probe could potentially result in an indictment recommendation, and it would then fall to Attorney General Loretta Lynch to decide whether to prosecute.

Morgan ChalfantEmail Morgan | Full Bio | RSSMorgan Chalfant is a staff writer at the Washington Free Beacon. Prior to joining the Free Beacon, Morgan worked as a staff writer at Red Alert Politics. She also served as the year-long Collegiate Network fellow on the editorial page at USA TODAY from 2013-14. Morgan graduated from Boston College in 2013 with a B.A. in English and Mathematics. Her Twitter handle is @mchalfant16.